How do I identify BB type?

glanma
glanma Posts: 36
edited July 2011 in Road beginners
I am intending to swop my 53/39 for 50/34 crankset along with a medium cage rear mech and bigger range sprocket set to help manage my dodgy knee on the hills around my area and some upcoming sportives. I have been looking at the various cranksets but am not sure what type of BB my bike has. It's a Fausto Coppi Gavia from I believe about 2002/3 with internal BB shells. Short of taking the crankset and BB apart (which i don't really want to do just for identification purposes as its my daily ride), how do I identify what BB type I would need to go with a new crankset? Sorry if its bit of a dim question but I'm trying to teach myself bike mechanics at the mo and haven't sussed this aspect of it out yet!!! :?

Comments

  • nicklouse
    nicklouse Posts: 50,675
    pics might help.

    also remove one of the bolt to help identify the fitting square taper/ISIS/Octalink...

    more info here:
    http://www.parktool.com/blog/repair-hel ... m-brackets
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • tim_wand
    tim_wand Posts: 2,552
    Do you mean Bottom Bracket thread type (I.E English 68mm and 73mm or Italian 70mm) or axle type and length.

    If its axle type (Square / isis/ octalink e.t.c ) as Nick says take off the non drive crank and look at the axle profile. as for length a general rule of thumb is 109-118 mm for a double/compact chainset and 113mm and beyond for a triple.

    You can measure the BB shell to find out if its Italian or English thread. It could be either as a Fausto Coppi Frame ( Although most are made in Taiwan and english Thread B/B)

    If your putting on a new chainset your just as well putting in a new bottom bracket anyway and there are not expensive compared to chainsets, Taking the old one out will tell you the exact type it was.

    If you buy a chainset and BB from an LBS theywill fit it for you most times, the expense as a private individual is usually buying a crank extractor and BB removal tool.
  • glanma
    glanma Posts: 36
    Ok - assuming I'm measuring the right place (!) I've got a 70mm BB shell (checked with a digital micrometer). Am I right in thinking this makes it Italian thread? And if so, what options should I look at for replacing the BB itself?
  • 2alexcoo
    2alexcoo Posts: 251
    glanma wrote:
    Ok - assuming I'm measuring the right place (!) I've got a 70mm BB shell (checked with a digital micrometer). Am I right in thinking this makes it Italian thread? And if so, what options should I look at for replacing the BB itself?

    Correct, 70mm indicates Italian thread.

    Most cranksets are designed to be used with a specific bottom bracket, so which one to buy depends on which crankset you end up buying. Eg for a Shimano Hollowtech II crankset, you would need a Shimano Hollowtech II BB in Italian thread.
    Alex
  • glanma
    glanma Posts: 36
    Gotcha! So, as I have got a sq.taper crankset with a seemingly ok bb its probably best to leave it as is and just find a suitable chainset. Unless of course I find for example a stunningly priced Hollowtech II, Octalink or whatever chainset in which case I need to match it with a similar BB - correct? (Online cycle mechanics courses for idiots - isn't it great eh?!!!) The only other problem I can see is that all the BB's I see advertised are external whereas mine is I think internal, ie. the face is flush with the BB shell. Are these a lot harder to come by?
  • nicklouse
    nicklouse Posts: 50,675
    nope and either type is interchangeable. (get the right threads) and if going from internal to external make sure you get the BB shell faced.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • glanma
    glanma Posts: 36
    Ok cheers all for the help - I am now feeling suitably 'enlightened'!

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